Air conditioner

ABSTRACT

An air conditioner which controls capacity of an outdoor heat-exchanger unit without an on-off valve that exhibits high pressure loss, which prevents accumulation of refrigerant in an outdoor heat-exchanger, and which maintains reliability of a compressor or refrigeration cycle. The air conditioner includes a first expansion valve on a liquid line of a first outdoor heat- exchanger, a second expansion valve on a liquid line of a second outdoor heat-exchanger, a first connection line to connect a suction line to one port of the first  4 -way valve, the suction line connecting a suction port of the compressor and an indoor heat-exchanger unit, a second connection line to connect the suction line to one port of the second  4 -way valve, and a check valve provided on the second connection line to allow flow of refrigerant only from the second  4 -way valve to the suction line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2012-0114473, filed on Oct. 15, 2012 in the Korean IntellectualProperty Office and of Japanese Patent Application No. 2011-271481,filed on Dec. 12, 2011 in the Japanese Intellectual Property Office, thedisclosures of which are incorporated herein by reference.

BACKGROUND

1. Field

Embodiments of the present disclosure relate to an air conditioner whichincludes an outdoor heat-exchanger unit constructed by connecting aplurality of outdoor heat-exchangers in a row, capacity of the outdoorheat-exchanger unit being controllable during low-load operation.

2. Description of the Related Art

For example, when an air conditioner is operated under low-loadoperating conditions, i.e. during heating operation under low indoorair-conditioning load and high outside temperature conditions or coolingoperation under low indoor air-conditioning load and low outsidetemperature, evaporation or condensation capability of an outdoorheat-exchanger excessively increases, causing problematic operation.More specifically, if evaporation capability of the outdoorheat-exchanger excessively increases during heating operation underlow-load operating conditions, discharge pressure of a compressor alsoexcessively increases to exceed an upper limit thereof, which causessudden shutdown of the compressor by a protective circuit. On the otherhand, if condensation capability of the outdoor heat-exchangerexcessively increases during cooling operation under low-load operatingconditions, discharge pressure of the compressor decreases and has onlya slight difference from suction pressure of the compressor, whichcauses an inappropriate compression ratio and makes it difficult tomaintain reliability of the compressor.

Accordingly, there has been proposed an air conditioner in which aplurality of outdoor heat-exchangers is connected in a row to constructan outdoor heat-exchanger unit such that capacity of the outdoorheat-exchanger unit is controllable based on operating conditions.

For example, Japanese Patent Publication No. H59-180251 discloses an airconditioner in which electronic on-off valves are provided at front andrear sides of respective outdoor heat-exchangers constituting an outdoorheat-exchanger unit, and each electronic valve is switched off to lowercapacity of the outdoor heat-exchanger unit under low-load operatingconditions.

However, the conventional air conditioner constructed as described abovemay suffer from high pressure loss during flow of refrigerant due to theplurality of electronic on-off valves provided at front and rear sidesof the respective outdoor heat-exchangers, thus deteriorating heating orcooling performance. However, using a large-scale electronic on-offvalve to reduce pressure loss may not be beneficial in terms of cost. Inaddition, although it may be contemplated to reduce the number ofelectronic on-off valves, for example, by installing the electronicon-off valve only at the front or rear side of each outdoorheat-exchanger, this may cause accumulation of refrigerant in theoutdoor heat-exchanger when the outdoor heat- exchanger is stopped, thusdeteriorating the flow rate of refrigerant and cooling or heatingperformance.

SUMMARY

It is an aspect of the present disclosure to provide an air conditionerwhich may control capacity of an outdoor heat-exchanger unit withoutusing an on-off valve that exhibits high pressure loss, preventaccumulation of refrigerant in an outdoor heat-exchanger when theoutdoor heat-exchanger is stopped, and maintain reliability of acompressor or refrigeration cycle.

Additional aspects of the disclosure will be set forth in part in thedescription which follows and, in part, will be apparent from thedescription, or may be learned by practice of the disclosure.

In accordance with one aspect of the disclosure, an air conditionerincludes a refrigerant circuit constructed via annular connection of acompressor, a 4-way valve unit, an outdoor heat-exchanger unit, and anindoor heat-exchanger unit, wherein the outdoor heat-exchanger unit isdivided into a first outdoor heat-exchanger and a second outdoorheat-exchanger, wherein the 4-way valve unit includes a first 4-wayvalve to switchably connect a gas line of the first outdoorheat-exchanger to any one of a discharge port or a suction port of thecompressor, and a second 4-way valve to switchably connect a gas line ofthe second outdoor heat-exchanger to any one of the discharge port orthe suction port of the compressor, and wherein the air conditionerincludes a first expansion valve provided on a liquid line of the firstoutdoor heat-exchanger, a second expansion valve provided on a liquidline of the second outdoor heat-exchanger, a first connection line toconnect a suction line and one port of the first 4-way valve to eachother, the suction line connecting the suction port of the compressorand the indoor heat exchanger unit to each other, a second connectionline to connect the suction line and one port of the second 4-way valveto each other, and a check valve provided on the second connection lineto allow flow of refrigerant only from the second 4-way valve to thesuction line.

Herein, the suction line may include a single suction line or aplurality of suction lines that connects the suction port of thecompressor and the indoor heat-exchanger unit to each other. There maybe examples in which the suction port of the compressor is connected toan accumulator via a single line and in turn the accumulator isconnected to the indoor heat- exchanger unit via a single line such thatthe suction line consists of two lines, and in which an additionalmember is connected between the suction port of the compressor and theindoor heat-exchanger unit and the suction line consists of a pluralityof lines.

With the above-described configuration, under low-load operatingconditions, the second expansion valve is closed and the second 4-wayvalve is switched to connect the gas line of the second outdoorheat-exchanger to the suction port of the compressor so as to preventrefrigerant from flowing to the second outdoor heat-exchanger, whichresults in reduction in the capacity of the outdoor heat-exchanger unit.In this way, it may be possible to control capacity of the outdoorheat-exchanger unit without providing a refrigerant circuit withelectronic on-off valves that exhibit high pressure loss, and to preventdeterioration in heating or cooling efficiency.

Although the electronic on-off valve is replaced by the two 4-wayvalves, no increase in cost occurs as compared to provision of alarge-scale electronic valve because the 4-way valve is a member easy torestrict increase in cost even if the size thereof increases to preventpressure loss.

As a result of providing the second connection line with the check valveto allow flow of refrigerant only from the second 4-way valve to thesuction line, it may be possible to prevent the refrigerant from thesuction line or the first connection line from accumulating in thesecond outdoor heat-exchanger through the second connection line evenwhen the refrigerant is not directed to the second outdoorheat-exchanger, but directed to the first outdoor heat-exchanger.Accordingly, it may be possible to prevent abnormal increase in thedischarge pressure of the compressor, or to prevent deterioration in thereliability of the compressor caused when a compression ratio is lessthan a predetermined value. Also, it may be possible to preventdeterioration in cooling performance due to accumulation of refrigerantin the second outdoor heat-exchanger when the second outdoorheat-exchanger is stopped.

As a detailed configuration to maintain a prescribed compression ratioby preventing excessive condensation capability of the outdoorheat-exchanger unit and reduction in the discharge pressure of thecompressor during cooling operation in which indoor air-conditioningload is low and outside temperature is low, the air conditioner mayfurther include a pressure meter to measure discharge pressure andsuction pressure of the compressor, and a valve controller to control atleast the second 4-way valve and the second expansion valve, and if acompression ratio that is a ratio of the discharge pressure to thesuction pressure measured by the pressure meter is less than apredetermined compression ratio during cooling operation, the valvecontroller may switch the second 4-way valve such that the gas line ofthe second outdoor heat-exchanger is connected to the suction port ofthe compressor, and the valve controller may also close the secondexpansion valve.

To prevent a high-pressure protection circuit from stopping thecompressor under conditions of excessive evaporation capability of theoutdoor heat-exchanger unit and increased discharge pressure of thecompressor during heating operation in which indoor air-conditioningload is low and outside temperature is high, the valve controller mayclose the second expansion valve if the discharge pressure measured bythe pressure meter is greater than a predetermined value during heatingoperation.

As a configuration to perform defrosting operation on each outdoorheat-exchanger, the 4-way valve unit may further include a main 4-wayvalve to switchably connect the indoor heat-exchanger unit to any one ofthe discharge port or the suction port of the compressor, the airconditioner may further include a first temperature sensor provided atthe first outdoor heat-exchanger, a second temperature sensor providedat the second outdoor heat-exchanger, a bypass line to connect theliquid line of the outdoor heat-exchanger unit and the suction line ofthe compressor to each other, an auxiliary heat-exchanger provided onthe bypass line to perform heat-exchange between refrigerant in theliquid line and refrigerant in the bypass line, and an auxiliaryexpansion valve provided on a liquid line of the auxiliaryheat-exchanger of the bypass line, the valve controller may beconfigured to control the first 4-way valve, the main 4-way valve andthe auxiliary expansion valve, and, if temperature detected by the firsttemperature sensor or the second temperature sensor is equal to or lessthan a predetermined value during heating operation in which the indoorheat-exchanger unit is connected to the discharge port of thecompressor, the valve controller may switch the first 4-way valve or thesecond 4-way valve such that the gas line of the first outdoorheat-exchanger or the second outdoor heat-exchanger is connected to thedischarge port of the compressor while maintaining the main 4-way valveto connect the indoor heat-exchanger unit and the discharge port of thecompressor to each other, thereby allowing gas-phase refrigerant to beintroduced into the first outdoor heat-exchanger or the second outdoorheat-exchanger, and the valve controller may also open the auxiliaryexpansion valve to allow liquid-phase refrigerant to be evaporated bythe auxiliary heat-exchanger and gas-phase refrigerant to return to thesuction line.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the disclosure will become apparent andmore readily appreciated from the following description of theembodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a schematic diagram illustrating an air conditioner duringcooling operation according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram illustrating the case in which capacity ofan outdoor heat- exchanger unit is reduced during cooling operation ofthe air conditioner according to the first- described embodiment of thepresent invention;

FIG. 3 is a graph illustrating variation of a compression ratio in thecase in which capacity of the outdoor heat-exchanger unit is reducedduring cooling operation of the air conditioner according to thefirst-described embodiment of the present disclosure;

FIG. 4 is a schematic diagram illustrating the air conditioner duringheating operation according to the first-described embodiment of thepresent disclosure;

FIG. 5 is a schematic diagram illustrating the case in which capacity ofthe outdoor heat- exchanger unit is reduced during heating operation ofthe air conditioner according to the first- described embodiment of thepresent disclosure;

FIGS. 6A and 6B are graphs illustrating variation of pressure in thecase in which capacity of the outdoor heat-exchanger unit is reducedduring heating operation of the air conditioner according to the relatedart and the first-described embodiment of the present disclosure,respectively;

FIG. 7 is a schematic diagram illustrating an air conditioner duringcooling operation according to another embodiment of the presentdisclosure;

FIG. 8 is a schematic diagram illustrating the case in which capacity ofan outdoor heat-exchanger unit is reduced during cooling operation ofthe air conditioner with according to the secondly-described embodimentof the present disclosure;

FIG. 9 is a schematic diagram illustrating the air conditioner duringheating operation according to the secondly-described embodiment of thepresent disclosure;

FIG. 10 is a schematic diagram illustrating the case in which capacityof the outdoor heat-exchanger unit is reduced during heating operationof the air conditioner according to the secondly-described embodiment ofthe present disclosure;

FIG. 11 is a diagram illustrating the concept of defrosting of the airconditioner according to the secondly-described embodiment of thepresent disclosure;

FIG. 12 is a schematic diagram illustrating a first defrosting operationof the air conditioner according to the secondly-described embodiment ofthe present disclosure;

FIG. 13 is a schematic diagram illustrating a second defrostingoperation of the air conditioner according to the secondly-describedembodiment of the present disclosure; and

FIG. 14 is a schematic diagram illustrating a third defrosting operationof the air conditioner according to the secondly-described embodiment ofthe present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout.

Configuration of First Embodiment

The first-described embodiment of the present disclosure will now bedescribed with reference to the drawings.

Referring to FIG. 1, an air conditioner, designated by reference numeral100, according to the first-described embodiment includes a refrigerantcircuit constructed by annular connection of a compressor 1, a 4-wayvalve unit 2, an outdoor heat-exchanger unit 3, and an indoorheat-exchanger unit 5. In the air conditioner 100, the 4-way valve unit2 is used to connect a connection for a discharge port or a suction portof the compressor 1 to any one of the outdoor heat-exchanger unit 3 orthe indoor heat-exchanger unit 5, such that each heat-exchanger unitfunctions as a condenser or an evaporator to enable selective switchingof room cooling and room heating. In the air conditioner 100 accordingto the first-described embodiment, to change heat-exchange capabilitiesof the outdoor heat-exchanger unit 3 based on outside temperature orindoor load, the 4-way valve unit 2 includes a first 4-way valve 21 anda second 4-way valve 22, and similarly the outdoor heat-exchanger unit 3is divided into a first outdoor heat-exchanger 31 and a second outdoorheat-exchanger 32. Additionally, an oil separator 6 is provided at thedischarge side of the compressor 1 to return oil collected by an oilcollecting line to the suction side of the compressor 1. An accumulator7 is located on a suction line L2 to allow only gas-phase refrigerantseparated from liquid-phase refrigerant to be suctioned into thecompressor 1. Additionally, the air conditioner 100 includes a controldevice 8 to control a variety of elements, such as the 4-way valve unit2 or expansion valves, and the like, that will be described hereinafter.

A connection configuration of the 4-way valve unit 2 and the outdoorheat-exchanger unit 3 will be described below based on cooling operationunder typical operating conditions illustrated in FIG. 1. Flow ofrefrigerant through each line will be represented by arrows on lines,and a closed state of the expansion valve will be represented by a blackcircle.

The refrigerant discharged from the discharge port of the compressor 1passes through the oil separator 6, and then is directed to two branchpaths, i.e. a first branch path and a second branch path. After passingthrough the 4-way valve, outdoor heat-exchanger and expansion valveprovided on each branch path, the refrigerant is merged and passesthrough the indoor heat-exchanger unit 5. The refrigerant having passedthrough the indoor heat- exchanger unit 5 reaches the suction line L2connected to the suction port of the compressor 1 by way of the first4-way valve 21, and is returned to the compressor 1.

More specifically, the first 4-way valve 21, first outdoorheat-exchanger 31, and first expansion valve 41 on a liquid line of thefirst outdoor heat-exchanger 31 are sequentially arranged in parallel onthe first branch path.

The first 4-way valve 21 switchably connects a gas line of the firstoutdoor heat-exchanger 31 to any one of the discharge port or thesuction port of the compressor 1. More specifically, a first port of thefirst 4-way valve 21 is connected to a discharge line L1 connected tothe discharge port of the compressor 1. The first 4-way valve 21 has asecond port connected to the gas line of the first outdoorheat-exchanger 31, a third port connected to a first connection line L31connected to the suction line L2 that is in turn connected to thesuction port of the compressor 1, and a fourth port connected to aliquid line of the indoor heat-exchanger unit 5.

In the case in which the first outdoor heat-exchanger 31 functions as acondenser and the first branch path functions as a cooling circuit, novoltage is applied to the first 4-way valve 21 to switch off the first4-way valve 21 such that the first port and the second port communicatewith each other and the third port and the fourth port communicate witheach other. On the other hand, in the case in which the first outdoorheat-exchanger 31 functions as an evaporator and the first branch pathfunctions as a heating circuit, voltage is applied to the first 4-wayvalve 21 to switch on the first 4-way valve 21 such that the first portand the fourth port communicate with each other and the second port andthe third port communicate with each other.

The second 4-way valve 22, second outdoor heat-exchanger 32, and secondexpansion valve 42 on a liquid line of the second outdoor heat-exchanger32 are sequentially arranged in parallel on the second branch path,similar to those as on the first branch path.

The second 4-way valve 22 switchably connects a gas line of the secondoutdoor heat-exchanger 32 to any one of the discharge port or thesuction port of the compressor 1, but this connection partially differsfrom that as in the first 4-way valve 21. More specifically, a firstport of the second 4-way valve 22 is connected to the discharge line L1connected to the discharge port of the compressor 1. The second 4-wayvalve 22 has a second port connected to the gas line of the secondoutdoor heat-exchanger 32, and a third port connected to a secondconnection line L32 connected to the suction line L2. Unlike the first4-way valve 21, a check valve 9 is provided on the second connectionline L32 to allow flow of the refrigerant only from the second 4-wayvalve 22 to the suction line L2, and a fourth port of the second 4-wayvalve 22 is closed. Providing the check valve 9 on the second connectionline L32 prevents the refrigerant in the suction line L2 from flowingbackward to the second outdoor heat-exchanger 32 through the second4-way valve 22 and from accumulating in the second outdoorheat-exchanger 32 when the second circuit serves as a heating circuit.

In the case in which the second outdoor heat-exchanger 32 functions as acondenser and the second branch path functions as a cooling circuit, novoltage is applied to the second 4-way valve 22 to switch off the second4-way valve 22 such that only the first port and the second portcommunicate with each other. Although the third port and the fourth portare connected to each other while the first port and the second portcommunicate with each other, the fourth port is closed, and therefore noflow of refrigerant occurs between the third port and the fourth port.On the other hand, in the case in which the second outdoorheat-exchanger 32 functions as an evaporator and the second branch pathfunctions as a heating circuit, voltage is applied to the second 4-wayvalve 22 to switch on the second 4-way valve 22 such that only thesecond port and the third port communicate with each other.

The control device 8 is a computer having a Control Processing Unit(CPU), memory, I/O channel, input/output device, AD/DA converter, or thelike. As the CPU or the peripheral device is operated based on a programstored in the memory, each component of the air conditioner 100 iscontrolled.

The control device 8 of the first-described embodiment at leastfunctions as a valve controller 81. The valve controller 81 controls atleast the second 4-way valve 22 and the second expansion valve 42 basedon a measured value of a pressure meter (not shown) that measuresdischarge pressure and suction pressure of the compressor 1, to preventdeterioration in the reliability of the compressor 1 caused when thecompressor 1 fails to maintain a prescribed compression ratio.Hereinafter, a configuration of the valve controller 81 as well asoperation of the air conditioner 100 will be described.

First, operation of the valve controller 81 will be described inrelation to the case in which the air conditioner 100 performs coolingoperation under lower-load conditions of low outside temperature and lowindoor load. Cooling operation of the air conditioner 100 according tothe first-described embodiment, as illustrated in FIG. 1, refers tooperation in which the first 4-way valve 21 and the second 4-way valve22 are in an off-state and both the first outdoor heat-exchanger 31 andthe second outdoor heat-exchanger 32 serve as a condenser.

Continuing cooling operation under low-load conditions may decreasedischarge pressure of the compressor 1, causing a small differencebetween the discharge pressure and suction pressure of the compressor 1.This makes it difficult for the compressor 1 to operate at a recommendedcompression ratio and causes breakdown of the compressor, for example.If the compression ratio that is a ratio of discharge pressure tosuction pressure measured by the pressure meter is less than apredetermined compression ratio during cooling operation, as illustratedin FIG. 2, the valve controller 81 switches the second 4-way valve 22such that the gas line of the second outdoor heat-exchanger 32 isconnected to the suction port of the compressor 1, and the valvecontroller 81 also closes the second expansion valve 42.

That is, if reduction in the compression ratio is detected, the valvecontroller 81 switches on the second 4-way valve 22 such that the firstport is connected to the fourth port and is closed while the second portand the third port communicate with each other. Since the secondexpansion valve 42 is closed by the valve controller 81, the secondbranch path on which the second outdoor heat-exchanger 32 is provided isseparated from the circuit, and no flow of the refrigerant occurs. Assuch, the refrigerant flows only through the first outdoor heat-exchanger 31, which allows capacity of the outdoor heat-exchanger unit 3to be reduced based on low-load conditions. Once capacity of the outdoorheat-exchanger unit 3 is reduced to conform to low-load conditions,discharge pressure of the compressor 1 increases as illustrated in thegraph of FIG. 3, which allows the compressor 1 to return from the lowcompression ratio to a normal compression ratio. In this way, thecompressor 1 may remain reliable.

Moreover, the check valve 9 provided on the second connection line L32may prevent the refrigerant, which returns from the indoorheat-exchanger unit 5 to the suction port 1 of the compressor 1 by wayof the fourth and third ports of the first 4-way valve 21, from flowingbackward to the second outdoor heat-exchanger 32. That is, when capacityof the outdoor heat- exchanger unit 3 is reduced based on low-loadconditions, it may be possible to prevent the refrigerant fromaccumulating in the second outdoor heat-exchanger 32 when the secondoutdoor heat-exchanger 32 is stopped, and to prevent deterioration incooling capability due to a lower flow rate of refrigerant.

Next, operation of the valve controller 81 will be described in relationto the case in which the air conditioner 100 performs heating operationunder low load conditions of high outside temperature and low indoorload. Also, to operate each outdoor heat-exchanger as an evaporatorduring heating operation of a typical output, each 4-way valve, asillustrated in FIG. 4, is switched such that the first port and thefourth port are connected to each other and the second port and thethird port communicate with each other, to ensure connection between thegas line of each outdoor heat-exchanger and the suction port of thecompressor 1.

Continuing heating operation under low load conditions, as illustratedin the graph of FIG. 6A, discharge pressure of the compressor 1continuously increases. Thus, for safety, operation of the compressor 1may stop by high-pressure protection. To prevent unwanted shutdown ofthe compressor 1, the valve controller 81, as illustrated in FIG. 5,closes the second expansion valve 42 if discharge pressure measured bythe pressure meter exceeds a predetermined value during heatingoperation. That is, the refrigerant having passed through the indoorheat-exchanger unit 5 passes through only the first heat-exchanger 31because the second expansion valve 42 is closed, which may reducecapacity of the outdoor heat-exchanger unit 3. If capacity of theoutdoor heat-exchanger unit 3 is reduced, as illustrated in FIG. 6B,discharge pressure of the compressor 1 decreases, which may preventexecution of a high-pressure protective circuit. Unlike theabove-described cooling operation, the second 4-way valve 22 remains inan original on-state during heating operation, and thus particularchange does not occur. Even in this case, owing to the check valve 9provided on the second connection line L32, it may be possible toprevent the refrigerant, which returns from the first outdoorheat-exchanger 31 to the suction port of the compressor 1 through thesuction line L2, from flowing backward from the second connection lineL32 and from accumulating in the second outdoor heat-exchanger 32.

Effects of First Embodiment

The air conditioner 100 according to the first-described embodiment hasthe effect of reducing capacity of the outdoor heat-exchanger unit 3based on low-load conditions of cooling operation or low load conditionsof heating operation by switching on or off the second 4-way valve 22and closing the second expansion valve 42. That is, it may beunnecessary to provide electronic on-off valves, which haveconventionally been employed to prevent flow of refrigerant through thesecond outdoor heat-exchanger 32, at front and rear sides of the secondoutdoor heat-exchanger 32.

Further, owing to providing the check valve 9 on the second connectionline L32 connected to the suction line L2, it may be possible to preventthe refrigerant from accumulating in the second outdoor heat-exchanger32, similar to using electronic on-off valves.

Accordingly, since electronic on-off valves that cause high pressureloss may be unnecessary to realize variable capacity of the outdoorheat-exchanger unit 3, and also since 4-way valves that exhibit lowpressure loss and are low cost despite a large size thereof may be used,it may be possible to prevent significant increase in manufacturingcosts without deterioration in the performance of a refrigerationcircuit.

Configuration of Second Embodiment

The air conditioner 100 according to the secondly-described embodimentof the present disclosure will now be described. Elements correspondingto those of the air conditioner 100 of the first-described embodimentwill be designated by the same reference numerals.

The air conditioner 100 of the secondly-described embodiment includesnot only a configuration for variable capacity of the outdoorheat-exchanger unit 3 via switching of flow of refrigerant to any one ofa plurality of outdoor heat-exchangers, but also a configuration fordefrosting of each outdoor heat-exchanger.

More specifically, the air conditioner 100 of the secondly-describedembodiment, as illustrated in FIG. 7, differs from the air conditioner100 of the first-described embodiment with respect to a configuration ofthe 4-way valve unit 2. Additionally, the air conditioner 100 of thesecondly-described embodiment further includes an auxiliaryheat-exchanger 33 provided on a bypass line L4 that connects the liquidline of the outdoor heat-exchanger unit 3 and the suction line L2 of thecompressor 1 to each other, and an auxiliary expansion valve 43 providedon a liquid line of the auxiliary heat-exchanger 33 of the bypass lineL4. Also, for defrosting, the valve controller 81 is changed inconfiguration to further control the first 4-way valve 21, a main 4-wayvalve 23 that will be described hereinafter, and the auxiliary expansionvalve 43.

Different elements from those of the first-described embodiment will bedescribed below in more detail.

The 4-way valve unit 2 includes the first 4-way valve 21, the second4-way valve 22, and the main 4-way valve 23 provided between the 4-wayvalves 21 and 22 and the discharge port of the compressor 1. The main4-way valve 23 switchably connects the gas line of the indoorheat-exchanger unit 5 to any one of the discharge port or the suctionport of the compressor 1. More specifically, a first port of the main4-way valve 23 is connected to the discharge line L1 connected to thedischarge port of the compressor 1. The main 4-way valve 23 has a secondport connected to the gas line of the indoor heat-exchanger unit 5, anda third port connected to the suction line L2 that is in turn connectedto the suction port of the compressor 1. A fourth port of the main 4-wayvalve 23 is closed. In a first state of the main 4-way valve 23, thefirst port and the second port communicate with each other and the thirdport and the fourth port communicate with each other. Also, in a secondstate of the main 4-way valve 23, the first port and the fourth portcommunicate with each other and the second port and the third portcommunicate with each other. The main 4-way valve 23 is switched suchthat the first port and the fourth port communicate with each otherduring cooling operation and the first port and the second portcommunicate with each other during heating operation.

Addition of the main 4-way valve 23 causes change in a connectionconfiguration of the first 4-way valve 21. The fourth port of the first4-way valve 21 is connected to the indoor heat-exchanger unit 5 in thefirst-described embodiment, but is closed in the secondly-describedembodiment. Also, to connect the first port of the first 4-way valve 21and the discharge port of the compressor 1 to each other, the dischargeline L1 is branched so as to be connected to the first port of the main4-way valve 23 and the first port of the first 4-way valve 21.

Even in the air conditioner 100 of the secondly-described embodimenthaving the above-described configuration, capacity of the outdoorheat-exchanger unit 3 may be appropriately changed even withoutproviding electronic on-off valves on the refrigerant circuit similar tothe first-described embodiment.

More specifically, if discharge pressure of the compressor 1 decreasesunder low-load conditions during cooling operation as illustrated inFIG. 7, the second 4-way valve 22 is switched to suit to a heating modeand is closed while the main 4-way valve 23 remains in a cooling mode toenable introduction of refrigerant from the indoor heat-exchanger unit 5as illustrated in FIG. 8.

Also, if discharge pressure of the compressor 1 excessively increasesunder low load conditions during heating operation as illustrated inFIG. 9, the second expansion valve 42 is closed while the main 4-wayvalve 23, the first 4-way valve 21 and the second 4-way valve 22 remainin a heating mode as illustrated in FIG. 10.

As such, similar to the first-described embodiment, it may be possibleto reduce capacity of the outdoor heat-exchanger unit as necessary, andto maintain a predetermined compression ratio or reduce dischargepressure of the compressor 1. Moreover, as a result of providing thecheck valve 9 on the second connection line L32, it may be possible toprevent the refrigerant from flowing backward from the suction line L2and from accumulating in the second outdoor heat-exchanger 32.

Next, defrosting of the air conditioner 100 during heating operationaccording to the secondly-described embodiment will be described.

During defrosting, as illustrated in FIG. 11, only the first outdoorheat-exchanger 31 is first subjected to defrosting, and then the firstoutdoor heat-exchanger 31 and the second outdoor heat-exchanger 32 aresimultaneously subjected to defrosting, and thereafter only the secondoutdoor heat-exchanger 32 is subjected to defrosting. Here, the valvecontroller 81 opens the auxiliary expansion valve 43 during simultaneousdefrosting of the first outdoor heat-exchanger 31 and the second outdoorheat-exchanger 32 to cause evaporation of liquid-phase refrigerant bythe auxiliary heat-exchanger 33 and allow gas-phase refrigerant toreturn to the suction line L2.

More specifically, if temperature detected by a first temperature sensor(not shown) or a second temperature sensor (not shown) is equal to orless than a predetermined value during heating operation, the valvecontroller 81, as illustrated in FIG. 12, first maintains the main 4-wayvalve 23 in a heating mode, switches the first 4-way valve 21 to suit toa cooling mode and maintains the second 4-way valve 22 in a heatingmode, thereby allowing gas-phase refrigerant to be introduced into thefirst outdoor heat-exchanger 31. In this way, defrosting of the firstoutdoor heat-exchanger 31 is achieved as high-temperature gas-phaserefrigerant is introduced into the first outdoor heat-exchanger 31. Thedefrosting of the first outdoor heat-exchanger 31 ends when temperaturedetected by the first temperature sensor becomes a predetermined valueor more (e.g., 1° C. or more). The auxiliary expansion valve 43 isclosed during defrosting of only the first outdoor heat-exchanger 31.

The valve controller 81 functions to delay detection of the firsttemperature sensor such that the detected temperature is acquired afterpredetermined time has passed from beginning of defrosting of the firstoutdoor heat-exchanger 31. Since the high-temperature gas-phaserefrigerant is introduced at once into the first outdoor heat-exchanger31 immediately after the first 4-way valve 21 is switched to begindefrosting, temperature detected by the first temperature sensor maytemporally show a sudden increase. Delaying detection of the firsttemperature sensor for a predetermined time (e.g., 60 seconds) mayprevent detection of an abnormally increased initial temperature.

Next, the valve controller 81, as illustrated in FIG. 13, simultaneouslyswitches the first 4-way valve 21 and the second 4-way valve 22 to suitto a cooling mode such that high-temperature gas-phase refrigerant isintroduced into the first outdoor heat-exchanger 31 and the secondoutdoor heat-exchanger 32 for a predetermined time T (e.g., 30 seconds),and the valve controller 81 also opens the auxiliary expansion valve 43for a predetermined time T (e.g., 30 seconds) such that liquid-phaserefrigerant is evaporated by the auxiliary heat-exchanger 33 to allowgas-phase refrigerant to return to the suction line L2.

Next, the valve controller 81, as illustrated in FIG. 14, switches thefirst 4-way valve 22 to suit to a heating mode, and maintains the second4-way valve 22 in a cooling mode, thereby allowing the gas-phaserefrigerant to be introduced into the second outdoor heat-exchanger 32.Thereby, defrosting of the second outdoor heat-exchanger 32 is achievedas high-temperature gas-phase refrigerant is introduced into the secondoutdoor heat-exchanger 32. The defrosting of the second outdoorheat-exchanger 32 ends when temperature detected by the secondtemperature sensor becomes a predetermined value or more (e.g., 1° C. ormore), and the second 4-way valve 22 is switched to suit to a heatingmode to enable implementation of typical heating operation. Theauxiliary expansion valve 43 is closed during defrosting of only thesecond outdoor heat-exchanger 32.

Effects of Second Embodiment

The air conditioner 100 according to the secondly-described embodimenthaving the above-described configuration may continuously implementheating operation even during defrosting by enabling alternatedefrosting of the first outdoor heat-exchanger 31 and the second outdoorheat-exchanger 32 while maintaining reliability of the compressor 1,which may restrict reduction of a room temperature during defrosting,and consequently create pleasant indoor environment.

Other embodiments may also be possible.

The refrigerant lines and connection methods of the respective 4-wayvalves according to the respective embodiments are given by way ofexample, and any other connection methods may be possible so long asthey enable switching of cooling and heating operations and prevent flowof refrigerant to a selected one of outdoor heat-exchangers.

Various variations and combinations of the embodiments may be permittedso long as they are not counter to the aims of the embodiments.

As is apparent from the above description, an air conditioner accordingto the embodiments of the present disclosure may adjust capacity of anoutdoor heat-exchanger unit based on low-load operating conditions using4-way valves and expansion valves without using electronic on-off valvesthat have difficulty in keeping balance of pressure loss and cost.Further, when introduction of refrigerant into a second outdoorheat-exchanger stops, it may be possible to prevent refrigerant from afirst connection line or a suction line from flowing backward through asecond connection line using a check valve provided on the secondconnection line and from accumulating in the second outdoorheat-exchanger when the second outdoor heat-exchanger is stopped.

Although the embodiments of the present disclosure have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

What is claimed is:
 1. An air conditioner comprising a refrigerantcircuit constructed via annular connection of a compressor, a 4-wayvalve unit, an outdoor heat-exchanger unit, and an indoor heat-exchangerunit, wherein the outdoor heat-exchanger unit is divided into a firstoutdoor heat-exchanger and a second outdoor heat-exchanger, wherein the4-way valve unit includes a first 4-way valve to switchably connect agas line of the first outdoor heat-exchanger to any one of a dischargeport or a suction port of the compressor, and a second 4-way valve toswitchably connect a gas line of the second outdoor heat-exchanger toany one of the discharge port or the suction port of the compressor, andwherein the air conditioner comprises a first expansion valve providedon a liquid line of the first outdoor heat-exchanger; a second expansionvalve provided on a liquid line of the second outdoor heat-exchanger; afirst connection line to connect a suction line and one port of thefirst 4-way valve to each other, the suction line connecting the suctionport of the compressor and the indoor heat exchanger unit to each other;a second connection line to connect the suction line and one port of thesecond 4-way valve to each other; and a check valve provided on thesecond connection line to allow flow of refrigerant only from the second4-way valve to the suction line.
 2. The air conditioner according toclaim 1, further comprising: a pressure meter to measure dischargepressure and suction pressure of the compressor; and a valve controllerto control at least the second 4-way valve and the second expansionvalve, wherein, if a compression ratio that is a ratio of the dischargepressure to the suction pressure measured by the pressure meter is lessthan a predetermined compression ratio during cooling operation, thevalve controller switches the second 4-way valve such that the gas lineof the second outdoor heat-exchanger is connected to the suction port ofthe compressor, and the valve controller also closes the secondexpansion valve.
 3. The air conditioner according to claim 2, whereinthe valve controller closes the second expansion valve if the dischargepressure measured by the pressure meter is greater than a predeterminedvalue during heating operation.
 4. The air conditioner according toclaim 1, wherein the 4-way valve unit further includes a main 4-wayvalve to switchably connect the indoor heat-exchanger unit to any one ofthe discharge port or the suction port of the compressor, wherein theair conditioner further comprises a first temperature sensor provided atthe first outdoor heat-exchanger; a second temperature sensor providedat the second outdoor heat-exchanger; a bypass line to connect theliquid line of the outdoor heat-exchanger unit and the suction line ofthe compressor to each other; an auxiliary heat-exchanger provided onthe bypass line to perform heat-exchange between refrigerant in theliquid line and refrigerant in the bypass line; and an auxiliaryexpansion valve provided on a liquid line of the auxiliaryheat-exchanger of the bypass line, wherein the valve controller isconfigured to control the first 4-way valve, the main 4-way valve andthe auxiliary expansion valve, and wherein, if temperature detected bythe first temperature sensor or the second temperature sensor is equalto or less than a predetermined value during heating operation in whichthe indoor heat-exchanger unit is connected to the discharge port of thecompressor, the valve controller switches the first 4-way valve or thesecond 4-way valve such that the gas line of the first outdoorheat-exchanger or the second outdoor heat-exchanger is connected to thedischarge port of the compressor while maintaining the main 4-way valveto connect the indoor heat-exchanger unit and the discharge port of thecompressor to each other, thereby allowing gas-phase refrigerant to beintroduced into the first outdoor heat-exchanger or the second outdoorheat-exchanger, and the valve controller also opens the auxiliaryexpansion valve to allow liquid-phase refrigerant to be evaporated bythe auxiliary heat-exchanger and gas-phase refrigerant to return to thesuction line.
 5. The air conditioner according to claim 2, wherein the4-way valve unit further includes a main 4-way valve to switchablyconnect the indoor heat-exchanger unit to any one of the discharge portor the suction port of the compressor, wherein the air conditionerfurther comprises a first temperature sensor provided at the firstoutdoor heat-exchanger; a second temperature sensor provided at thesecond outdoor heat-exchanger; a bypass line to connect the liquid lineof the outdoor heat-exchanger unit and the suction line of thecompressor to each other; an auxiliary heat-exchanger provided on thebypass line to perform heat-exchange between refrigerant in the liquidline and refrigerant in the bypass line; and an auxiliary expansionvalve provided on a liquid line of the auxiliary heat-exchanger of thebypass line, wherein the valve controller is configured to control thefirst 4-way valve, the main 4-way valve and the auxiliary expansionvalve, and wherein, if temperature detected by the first temperaturesensor or the second temperature sensor is equal to or less than apredetermined value during heating operation in which the indoorheat-exchanger unit is connected to the discharge port of thecompressor, the valve controller switches the first 4-way valve or thesecond 4-way valve such that the gas line of the first outdoorheat-exchanger or the second outdoor heat-exchanger is connected to thedischarge port of the compressor while maintaining the main 4-way valveto connect the indoor heat-exchanger unit and the discharge port of thecompressor to each other, thereby allowing gas-phase refrigerant to beintroduced into the first outdoor heat-exchanger or the second outdoorheat-exchanger, and the valve controller also opens the auxiliaryexpansion valve to allow liquid-phase refrigerant to be evaporated bythe auxiliary heat-exchanger and gas-phase refrigerant to return to thesuction line.
 6. The air conditioner according to claim 3, wherein the4-way valve unit further includes a main 4-way valve to switchablyconnect the indoor heat-exchanger unit to any one of the discharge portor the suction port of the compressor, wherein the air conditionerfurther comprises a first temperature sensor provided at the firstoutdoor heat-exchanger; a second temperature sensor provided at thesecond outdoor heat-exchanger; a bypass line to connect the liquid lineof the outdoor heat-exchanger unit and the suction line of thecompressor to each other; an auxiliary heat-exchanger provided on thebypass line to perform heat-exchange between refrigerant in the liquidline and refrigerant in the bypass line; and an auxiliary expansionvalve provided on a liquid line of the auxiliary heat-exchanger of thebypass line, wherein the valve controller is configured to control thefirst 4-way valve, the main 4-way valve and the auxiliary expansionvalve, and wherein, if temperature detected by the first temperaturesensor or the second temperature sensor is equal to or less than apredetermined value during heating operation in which the indoorheat-exchanger unit is connected to the discharge port of thecompressor, the valve controller switches the first 4-way valve or thesecond 4-way valve such that the gas line of the first outdoorheat-exchanger or the second outdoor heat-exchanger is connected to thedischarge port of the compressor while maintaining the main 4-way valveto connect the indoor heat-exchanger unit and the discharge port of thecompressor to each other, thereby allowing gas-phase refrigerant to beintroduced into the first outdoor heat-exchanger or the second outdoorheat-exchanger, and the valve controller also opens the auxiliaryexpansion valve to allow liquid-phase refrigerant to be evaporated bythe auxiliary heat-exchanger and gas-phase refrigerant to return to thesuction line.
 7. An air conditioner comprising: a compressor; a 4-wayvalve unit including a first 4-way valve and a second 4-way valve; anoutdoor heat-exchanger unit including a first outdoor heat-exchanger anda second outdoor heat-exchanger; and an indoor heat-exchanger unit,wherein the first 4-way valve is configured to switchably connect a gasline of the first outdoor heat-exchanger to any one of a discharge portor a suction port of the compressor, and the second 4-way valve isconfigured to switchably connect a gas line of the second outdoorheat-exchanger to any one of the discharge port or the suction port ofthe compressor.
 8. The air conditioner according to claim 7, furthercomprising: a first expansion valve provided on a liquid line of thefirst outdoor heat-exchanger; a second expansion valve provided on aliquid line of the second outdoor heat-exchanger; a first connectionline to connect a suction line and one port of the first 4-way valve toeach other, the suction line connecting the suction port of thecompressor and the indoor heat exchanger unit to each other; a secondconnection line to connect the suction line and one port of the second4-way valve to each other; and a check valve provided on the secondconnection line to allow flow of refrigerant only from the second 4-wayvalve to the suction line.
 9. The air conditioner according to claim 7,wherein the suction line includes a plurality of suction lines thatconnect the suction port of the compressor and the indoor heat-exchangerunit to each other.
 10. The air conditioner according to claim 7,wherein the suction port of the compressor is connected to anaccumulator via a single line and the accumulator is connected to theindoor heat-exchanger unit via a single line, and an additional memberis connected between the suction port of the compressor and the indoorheat-exchanger unit.
 11. The air conditioner according to claim 8,further comprising: a pressure meter to measure discharge pressure andsuction pressure of the compressor; and a valve controller to control atleast the second 4-way valve and the second expansion valve, and if acompression ratio that is a ratio of the discharge pressure to thesuction pressure measured by the pressure meter is less than apredetermined compression ratio during cooling operation, the valvecontroller is configured to switch the second 4-way valve such that thegas line of the second outdoor heat-exchanger is connected to thesuction port of the compressor, and the valve controller closes thesecond expansion valve.
 12. The air conditioner according to claim 8,wherein the 4-way valve unit further comprises a main 4-way valve toswitchably connect the indoor heat-exchanger unit to any one of thedischarge port or the suction port of the compressor.
 13. The airconditioner according to claim 12, further comprising: a firsttemperature sensor provided at the first outdoor heat-exchanger; asecond temperature sensor provided at the second outdoor heat-exchanger;a bypass line to connect the liquid line of the outdoor heat-exchangerunit and the suction line of the compressor to each other; an auxiliaryheat-exchanger provided on the bypass line to perform heat-exchangebetween refrigerant in the liquid line and refrigerant in the bypassline; and an auxiliary expansion valve provided on a liquid line of theauxiliary heat-exchanger of the bypass line, wherein the valvecontroller is configured to control the first 4-way valve, the main4-way valve and the auxiliary expansion valve, and, if the temperaturedetected by the first temperature sensor or the second temperaturesensor is equal to or less than a predetermined value during heatingoperation in which the indoor heat-exchanger unit is connected to thedischarge port of the compressor, the valve controller is configured toswitch the first 4-way valve or the second 4-way valve such that the gasline of the first outdoor heat-exchanger or the second outdoorheat-exchanger is connected to the discharge port of the compressorwhile maintaining the main 4-way valve to connect the indoorheat-exchanger unit and the discharge port of the compressor to eachother, thereby allowing gas-phase refrigerant to be introduced into thefirst outdoor heat-exchanger or the second outdoor heat-exchanger, andthe valve controller is configured to open the auxiliary expansion valveto allow liquid-phase refrigerant to be evaporated by the auxiliaryheat-exchanger and gas-phase refrigerant to return to the suction line.